The invention relates to a method for coding human speech for subsequent reproduction thereof. Generally, methods based on the principles of LPC-coding will produce speech of only moderate quality. The present inventor has found that the principles of LPC coding represent a good starting point for seeking further improvement. In particular, the values of LPC filter characteristics may be adapted, to get a better result if the various influences thereof on speech generation are taken into account in a more refined manner.
Such method has been disclosed in A. Rosenberg, (1971), Effect of Glottal Pulse Shape on the Quality of Natural Vowels, Journal of the Acoustical Society of America 49, 583-590. From a computational point of view this method is extremely straightforward, in that the expressions for the glottal pulse flow and its time derivative are explicit in the relevant parameters. The results however have been found insufficient, both from a psychoacoustic and also from a speech production point of view, in that various generation parameters could not be chosen in an optimal manner. In particular, this is caused by the absence of a return phase in the glottal pulse response curve.